Js lazy fetch with getter

lazy-fetch-with-getter.js

const wait = s => new Promise((resolve) => setTimeout(resolve, s * 1000))

const state = {};
dataField(state, "ip", "http://ip.jsontest.com/");

console.log(state.ip);

wait(2)
 .then(() => state.ip)
 .then(console.log);

// {pending: true, value: null, error: null}
// ..
// {pending: false, value: "185.36.49.253", error: null}

function dataField (state, field, url) {

  const data = {
    pending: false,
    value: null,
    error: null,
  };

  Object.defineProperty(state, field, {

    get() {
      if (data.value == null && !data.pending) {
        data.pending = true;

        fetch(url)
          .then(res => res.json())
   	  .then(res => res.ip)
          .then(ip => {
	    data.value = ip;
            data.pending = false;
          })
          .catch(error => data.error = error);
      }

      return data;
    } 
  });

};

// {pending: true, value: null, error: null}
// ..
// {pending: false, value: "185.36.49.253", error: null}